Abstract: The range of plastic zone and support deformation of the surrounding rock of roadway are obtained by combining with the derivation method of plastic solution of surrounding rock of roadway and the Hoek Brown strength criteria considering the intermediate principal stress.According to the results of the theoretical derivation,radius of plastic zone of surrounding rock of roadway and the expression of displacement are acquired.In addition,the plasticity index has the relationship with the initial two-dimensional compressive stress of surrounding rock,rock mass quality,parameters of geological engineering and the supporting reaction force.The Hoek-Brown strength criteria considering the intermediate principal stress has the qualification to analyze the plastic zone of surrounding rock of roadway so as to acquire more accurate results.Therefore,the above research results is conducive to the engineering practice.

Key words: Hoek-Brown strength criteria, Intermediate principal stress, Plasticity index